1. Field of the Invention
The present invention relates to a face detection device configured to detect the face of a person in an input image, an imaging apparatus including the function of the face detection device, and a face detection method.
2. Description of the Related Art
In recent years, the use of digital imaging apparatuses including digital still cameras and digital video cameras has been rapidly increasing, and these apparatuses are becoming more sophisticated. This has been resulted in a growing demand for more advanced functions to be included in these apparatuses, whereby the commercial value thereof can be enhanced. An exemplary advanced function that has been the focus in this field is the technique of detecting a specific object in an image.
A representative technique of detecting an object is the technique of detecting the face of a person. With this face detection technique, a face area of a person can be extracted from a captured image, and the extraction result may be applied to various applications in the imaging apparatus or may be recorded as accompanying data of the image.
A known exemplary face detection technique involves conversion of captured image data into luminance data, hue data, and chroma data, and detection of a face area of a person on the basis of a change in luminance in the vertical direction in a skin-color area based on the luminance data and a spatial pixel distribution of skin-color pixels based on the three attribute data (for example, see Japanese Patent No. 3561985, paragraphs [0038] to [0058], FIG. 1). Another known exemplary technique involves detection of a skin-color area and face feature points, such as the eyes and the mouth, in a captured image and determination of whether the skin-color area is the face of a person on the basis of the positions of the feature points (for example, see Japanese Unexamined Patent Application Publication No. 2004-5384, paragraphs and [0019], FIG. 1). Yet another known exemplary technique that does not particularly use color information involves the matching of a captured image with a face template image using luminance data of the captured image and, in the case where a correlation value between the two images is sufficiently high, it is determined that the captured image is an image of a face (for example, see Japanese Unexamined Patent Application Publication No. 2003-271933, paragraphs [0046] to [0055], FIG. 6).